Injuries to the anterior cruciate ligament (ACL) are a common risk in skiing. Understanding the causes and risk factors of this injury, as well as the correct prevention strategies, is crucial to reduce the risk and increase safety on the slopes. In this blog article, we will explain the most important aspects of ACLs in skiing and how to effectively protect yourself from them
Facts and figures: How common is a cruciate ligament rupture in skiing?
20.9% of all injuries that occur in skiing involve the ACL. A meta-analysis, which examined all incidence studies on cruciate ligament ruptures in skiing, showed that out of 6 million recreational skiers, more than 3000 suffered a cruciate ligament rupture - this corresponds to a frequency of 0.05%. Compared to other sports such as football or basketball, this figure is twice to three times as high. For professional skiers, however, this figure is significantly lower. Interestingly, recreational skiers are more affected than professional skiers, suggesting that technique and experience play a significant role.
The frequency of cruciate ligament ruptures is much lower among snowboarders. Only 2.4% of all injuries affect the cruciate ligament. Wrist or shoulder injuries are much more common here.20.9% of all injuries that occur in skiing affect the cruciate ligament. A meta-analysis, which examined all incidence studies on cruciate ligament ruptures in skiing, showed that out of 6 million recreational skiers, more than 3000 suffered a cruciate ligament rupture - this corresponds to a frequency of 0.05%. Compared to other sports such as football or basketball, this figure is twice to three times as high. For professional skiers, however, this figure is significantly lower. Interestingly, recreational skiers are more affected than professional skiers, suggesting that technique and experience play a significant role.
The frequency of cruciate ligament ruptures is much lower among snowboarders. Only 2.4% of all injuries affect the cruciate ligament. Wrist or shoulder injuries are much more common here.
Causes and triggers of the crack
Position and function of the cruciate ligaments
There are two cruciate ligaments in the knee joint: the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). They connect the femur to the tibia. The anterior cruciate ligament stabilizes the knee joint by limiting the displacement of the tibia in front as well as excessive internal rotations. Cruciate ligament ruptures occur most frequently in abrupt braking situations in which the leg is bent less than 30°. An additional X-leg position, also known as a "valgus" position, further increases the risk. If the knee is turned outwards at the same time, this creates what is known as valgus stress. This is particularly common in sports such as skiing.
Internal and external risk factors - Am I at risk?
- Internal risk factors
Age:
With increasing age, the muscles decrease and the elasticity of the tissue decreases. This means that the body is less able to absorb shocks and stresses, making the cruciate ligament more susceptible to injury. The flexibility and stability of the knee are particularly affected, which increases the risk of a cruciate ligament rupture. Strong muscles remain the best protection for the cruciate ligament - and this is precisely why it is important to remain active even in old age.
Condition and muscle strength:
The thigh muscles, especially the hamstrings and quadriceps, play a crucial role in protecting the anterior cruciate ligament, as they actively support the stability of the knee joint and reduce excessive strain on the ligament.
The hamstrings pull the shin backwards and prevent it from sliding forwards. During quick stops, landings or changes of direction, the hamstrings stabilize the knee and reduce the risk of injury to the cruciate ligament.
In contrast, the quadriceps pulls the tibia forward, which can increase the load on the cruciate ligament. The quadriceps have a particularly strong effect on the cruciate ligament tension at an angle of approx. 20-30° flexion.
An imbalance between excessively strong quadriceps and weak hamstrings can therefore significantly increase the risk of an ACL tear.
However, the active interaction of the quadriceps and hamstrings is crucial for the "active stability" of the knee, as it relieves the passive stability provided by ligaments such as the anterior cruciate ligament. A lack of or delayed co-activation of these muscles can impair knee joint control and increase the risk of cruciate ligament injuries, especially during sudden loading or fatigue.
X-B setting
From a purely anatomical and biomechanical point of view, a knock-kneed position is a significant risk factor for a cruciate ligament rupture. The knee position can be checked with a simple single leg squat. The inward tilt of the knee during a single leg squat correlates with weak hip abductors.
Skill level
Beginners need to be particularly careful when skiing. They are not yet used to the forces and movements involved in skiing. The combination of poor technique, especially posture, and inefficient reaction to sudden stresses makes beginners more susceptible to cruciate ligament injuries. However, with targeted instruction and technique training, they can improve their neuromuscular control and significantly reduce the risk.
- External risk factors
Snow condition
Fresh snow and icy slope conditions increase the risk of a cruciate ligament rupture. The conditions change the interaction between skis and snow. In fresh snow, you quickly find yourself in a backward position, which increases the load on the quadriceps and therefore the load on the cruciate ligament.
Difficulty level of the slope
Surprisingly, skiing on easier slopes is associated with a higher risk of cruciate ligament injuries. This could be because skiers underestimate the risk and are less careful.
Concentration and fatigue
Insufficient concentration and fatigue increase the risk of a cruciate ligament rupture in skiing, as they impair reaction time, coordination and muscle activation. As a result, necessary protective mechanisms, such as the stabilization of the knee by the thigh muscles, cannot be activated effectively, which leads to increased strain on the cruciate ligament.
Fit for the slopes: Your protective shield against cruciate ligament injuries - How much can preventive training prevent?
Posture
A forward-leaning posture when skiing is safer as it reduces the load on the anterior cruciate ligament and at the same time activates the hamstrings muscles more strongly. In contrast, a backward-leaning posture increases the risk of cruciate ligament injuries as it places greater strain on the quadriceps muscles and thus increases the extension moment in the knee joint.
Training (3×3)
The term 3×3 is made up of strength training, coordination and plyometrics. These three areas, also known as neuromuscular training, each comprise three exercises aimed at optimally preparing the muscles for stress and counteracting a cruciate ligament rupture in the best possible way. The strength exercises focus in particular on strengthening the hip abductors, core stability and knee control through efficient neuromuscular activation of the hamstrings and quadriceps.
Strength training - Top Three
- Hip abductors
- Knee flexors
- Torso strength
1. hip abductors
2. knee flexors:
3. trunk strength:
Coordination - Top Three
Plyometrics - Top Three
If it has happened - surgery yes or no?
After a knee injury, the crucial question often arises: surgery or conservative treatment? There is no clear answer, as both approaches have advantages and disadvantages. Choosing the right method depends on factors such as age, sporting level and symptoms such as feelings of instability. Here is an overview to help you decide.
To summarize:
In one study, patients with early cruciate ligament surgery and those with conservative therapy, each combined with rehabilitation, were compared. There were no significant differences in subjective knee function between the groups after two and five years. However, the surgery reduced the feeling of instability and led to a more frequent return to sport, while the conservative group showed a lower risk of osteoarthritis-like changes.
Any questions?
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Sources:
Websites:
https://www.bauerfeind.de/de/gesundheit/knie/knieschmerzen/kreuzbandriss#c22373
https://www.stop-x.de/wp-content/uploads/2021/02/2020_StopX-Redesign_BroschuereA6.pdf
https://www.hirslanden.ch/de/corporate/krankheitsbilder/kreuzbandriss.html
https://flexikon.doccheck.com/de/Vorderes_Kreuzband
Papers:
Hashemi, J., Breighner, R., Chandrashekar, N., Hardy, D. M., Chaudhari, A. M., Shultz, S. J., Slauterbeck, J. R., & Beynnon, B. D. (2011). Hip extension, knee flexion paradox: A new mechanism for non-contact ACL injury. Journal of Biomechanics, 44(4), 577-585. https://doi.org/10.1016/j.jbiomech.2010.11.013
Mehl, J., Diermeier, T., Herbst, E., Imhoff, A. B., Stoffels, T., Zantop, T., Petersen, W., & Achtnich, A. (2018). Evidence-based concepts for prevention of knee and ACL injuries. 2017 guidelines of the ligament committee of the German Knee Society (DKG). Archives of Orthopaedic and Trauma Surgery, 138(1), 51-61. https://doi.org/10.1007/s00402-017-2809-5
Monk, A. P., Davies, L. J., Hopewell, S., Harris, K., Beard, D. J., & Price, A. J. (2016). Surgical versus conservative interventions for treating anterior cruciate ligament injuries. Cochrane Database of Systematic Reviews, 4. https://doi.org/10.1002/14651858.CD011166.pub2
Posch, M., Ruedl, G., Greier, K., Faulhaber, M., Tecklenburg, K., Schranz, A., Schliernzauer, B., & Burtscher, M. (2023). Impact of Environmental Factors on the ACL Injury Risk in Recreational Alpine Skiing. International Journal of Sports Medicine, 44(13), 1003-1008. https://doi.org/10.1055/a-2134-3908
Prodromos, C. C., Han, Y., Rogowski, J., Joyce, B., & Shi, K. (2007). A Meta-analysis of the Incidence of Anterior Cruciate Ligament Tears as a Function of Gender, Sport, and a Knee Injury-Reduction Regimen. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 23(12), 1320-1325.e6. https://doi.org/10.1016/j.arthro.2007.07.003
Snowboarding Injuries. (n.d.). https://doi.org/10.1177/0363546511433279
(Prodromos et al., 2007)
(Mehl et al., 2018)
(Hashemi et al., 2011)
(Posch et al., 2023)
(Snowboarding Injuriesn.d.)
(Monk et al., 2016)
